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During the standardization of KMnO4, if you observe a brown precipitate, what does this indicate? What would you do in this situation?
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+ Precipitation
+ Chemistry
+ Potassium permanganate
Posted by
Muiz Roslin
During the standardization of KMnO4, if you observe a brown precipitate, what does this indicate? What would you do in this situation?
If the titration is done without enough sulfuric acid or it is done very quickly it is possible to get MnO2 which forms the brown ppt. Adding more sulfuric acid might clear it.
If the titration is done without enough sulfuric acid or it is done very quickly it is possible to get MnO2 which forms the brown ppt. Adding more sulfuric acid might clear it.
It is probably insoluble MnO2. The standardization is supposed to reduce MnO4 (-) to Mn(+2), ie a reduction of Mn from oxidation +7 to +2. The presence of MnO2 suggests some of the manganese has been reduced from +7 to +4, thereby invalidating the standardization. Check the original solutions for impurities, especially the presence of MnO2 in the KMNO4. This can happen on aging or exposure to strong light, and is often indicated by a discoloration of the glass container in which the reagent is being stored. If the MnO2 is present in suspension in the reagent it may not show until near the end of a titration because of the intense colour of the MNO4(-) ion.
It is probably insoluble MnO2. The standardization is supposed to reduce MnO4 (-) to Mn(+2), ie a reduction of Mn from oxidation +7 to +2. The presence of MnO2 suggests some of the manganese has been reduced from +7 to +4, thereby invalidating the standardization. Check the original solutions for impurities, especially the presence of MnO2 in the KMNO4. This can happen on aging or exposure to strong light, and is often indicated by a discoloration of the glass container in which the reagent is being stored. If the MnO2 is present in suspension in the reagent it may not show until near the end of a titration because of the intense colour of the MNO4(-) ion.
If the titration is done without enough sulfuric acid or it is done very quickly it is possible to get MnO2 which forms the brown ppt. Adding more sulfuric acid might clear it.
If the titration is done without enough sulfuric acid or it is done very quickly it is possible to get MnO2 which forms the brown ppt. Adding more sulfuric acid might clear it.
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It is probably insoluble MnO2. The standardization is supposed to reduce MnO4 (-) to Mn(+2), ie a reduction of Mn from oxidation +7 to +2. The presence of MnO2 suggests some of the manganese has been reduced from +7 to +4, thereby invalidating the standardization. Check the original solutions for impurities, especially the presence of MnO2 in the KMNO4. This can happen on aging or exposure to strong light, and is often indicated by a discoloration of the glass container in which the reagent is being stored. If the MnO2 is present in suspension in the reagent it may not show until near the end of a titration because of the intense colour of the MNO4(-) ion.
It is probably insoluble MnO2. The standardization is supposed to reduce MnO4 (-) to Mn(+2), ie a reduction of Mn from oxidation +7 to +2. The presence of MnO2 suggests some of the manganese has been reduced from +7 to +4, thereby invalidating the standardization. Check the original solutions for impurities, especially the presence of MnO2 in the KMNO4. This can happen on aging or exposure to strong light, and is often indicated by a discoloration of the glass container in which the reagent is being stored. If the MnO2 is present in suspension in the reagent it may not show until near the end of a titration because of the intense colour of the MNO4(-) ion.
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